Removal of wax from hydrocarbon oil



Patented Jan. 7, 1936 UNITED STATES PATENT OFFICE REMOVAL OF WAX FROM HYDROCARBON OIL tion of Delaware No Drawing. Application November 30, 1931, Serial No. 578,208

9 Claims.

This invention relates to the removal of wax from hydrocarbons and more particularly to an improved process for the removal of paraflin from lubricating oil fractions derived from petroleum.

The invention contemplates a process of dewaxing wax-containing lubricating oil fractions by filtration at low temperatures, wherein the wax-containing oil is mixed with a wax-precipitating liquid medium composed of a solvent liquid or mixture of solvent liquids which is completely miscible with, and exerts a substantially complete solvent action upon, the oil at the temperatures at which the wax constituents are precipitated from the oil in solid form and which has substantially no solvent action on the solid hydrocarbons at such temperatures. The resulting mixture is then chilled to precipitate the solid hydrocarbons which are removed by filtration.

More specifically the invention contemplates mixing with lubricating oil fractions 2. wax-precipitating liquid medium composed of a mixture of propylene dichloride with ethylene-glycolmono ethylether or diethylene-glycolmonobutyl-ether.

An object of this invention is to effect dewaxing of parafiin-containing hydrocarbon oils with an improved type of solvent liquid composed of a mixture of solvents having selective solvent properties between the oil and the wax constituents and which, in addition, retains its selective solvent properties at relatively low temperatures whereby the precipitation of the wax from the mixture, particularly in the case of mixtures with relatively viscous oils, is effected in a more readily filterable form. At the same time, a high yield of dewaxed oil is obtained.

A further object has been to develop a solvent liquid which possessed the foregoing properties at relatively low temperatures and which is, therefore, adaptable for the manufacture of lubricating oils having pour tests of -20 F. and lower.

A selective solvent suitable for the foregoing dewaxing operation, and particularly when composed of two or more organic solvents, must retain its homogeneity and its property of remaining completely miscible with the liquid hydrocarbonconstituents of the mineral oil at temperatures substantially well below 0 F. Complete miscibility is necesary in order to prevent sep-- aration of such liquid hydrocarbons from the solution. Such separated liquid hydrocarbons materially increase the viscosity of the solution thereby tending to reduce the filtering rate to a point where the operation is not economical. In

addition, the presence of this separated liquid gives rise to a condition which is productive upon filtration of a wax cake containing substantial amounts of oil so that the maximum yield of dewaxed oil is not realized. 5.

It is essential that such a solvent mixture remain completely homogeneous at these low temperatures and not exhibit any tendency for any of its components to separate from the mixture.

Upon separation of one of the components from 10..

cipitated and/or appreciable amounts of the 15.

liquid hydrocarbon may separate from the solution due to the resulting lack of complete miscibility on the part of the solvent with the oil owing to its altered condition.

Extensive investigation has demonstrated that 20 a solvent liquid or solvent mixture satisfactory for use as a wax-precipitating medium in the dewaxing of wax-containing hydrocarbon oils must possess, among other things, low absolute viscosity and low viscosity temperature coefficient, high oil 25 solubility at low temperatures, low wax solubility at low temperatures, low freezing point, and also possess the property of precipitating wax in a. readily filterable condition.

Accordingly after investigating various solvent 30 liquid mixtures, it has been found that a mixture of propylene dichloride and ethylene-glycolmono-ethyl-ether or diethylene-glycol-monobutyl-ether possesses the foregoing combination of properties, thereby rendering it superior to the 35 solvent liquids or liquid mixtures hitherto used in the art and, therefore, particularly well adapted as a wax-precipitating medium for use in the manufacture of low pour test paraffin base lubricating oil. The relative proportion of these 40 liquids to each other, as well as that of the resulting solvent mixture to the oil, may be varied as desired, depending upon the nature of the oil undergoing treatment.

Thus when dewaxing a lubricating distillate fraction having a viscosity of around '70 to 80 Saybolt Universal seconds or higher at 210 F., about thirty parts of the oil may be mixed with about seventy parts of a solvent mixture composed of around 80% propylene dichloride and about 20% of either ethylene-glycol-mono-ethylether or diethylene glycol mono butyl ether. The resulting mixture is then chilled to about 10 F. or to a temperature corresponding substantially to the desired pour test of the resulting dewaxed oil, following which it is subjected to filtration while still maintained in a cold condition to separate the precipitated wax constituents. Advantageously filtration may be carried out in the presence of a cornminuted filter-aid material which may be added to the cold mixture of oil, solvent and suspended wax crystals. After removal of the solvent liquid from the filtrate, the resulting lubricting oil will have a pour test of 0 F. or lower.

While the use of the foregoing solvent liquid mixtures has been described in connection with a lubricating distillate fraction of relatively high viscosity, it is contemplated that mixtures of these solvent liquids may be equally well employed with oils of various viscosity range. It is also contemplated that mixtures of these solvent liquids are not necessarily restricted to dewaxing distillate fractions but may also be used in dewaxing various wax-bearing fractions of mineral oil.

Obviously many modifications and variations of the invention, as hereinbefore set forth, may be made without departing from the spirit and scope thereof, and therefore only such limitations should be imposed as are indicated in the appended claims.

We claim:

1. In the process of manufacturing low pour test lubricating oil from wax-bearing mineral oil substantially as described, the step of treating oil with a solvent to precipitate wax constituents comprising mixing with the oil a selective solvent liquid composed of propylene dichloride in admixture with a liquid selected from the group consisting of ethylene-glycol-mono-ethyl-ether and diethylene-glycol-mono-butyl-ether, in such proportions that at temperatures of 10 F. or lower, the solvent has substantially complete solvent action on the oil and substantially no solvent action on the wax.

2. In the process of manufacturing low pour test lubricating oil from wax-bearing mineral oil substantially as described, the step of treating the oil with a solvent to precipitate wax constituents comprising mixing with the oil a selective solvent liquid composed of propylene dichloride in admixture with ethylene-glycol-mono-ethyl-ether, in which the propylene dichloride is at least equal in volume to the ether.

3. In the process of manufacturing low pour test lubricating oil from Wax-bearing mineral oil substantially as described, the step of treating the oil with a solvent to precipitate wax constituents comprising mixing with the oil a selective solvent liquid composed of propylene dichloride in admixture with diethylene-glycol-monobutyl-ether, in which the propylene dichloride is at least equal in volume to the ether.

4. The process of manufacturing lubricating oil having a pour test of 0 F. or lower from a waxbearing mineral oil which comprises mixing the oil with a selective solvent liquid composed of propylene dichloride and a liquid selected from the group consisting of ethylene-glycol-monoethyl-ether and diethylene-glycol-mono-butylether in such proportions that at temperatures of 10 F. or lower, the solvent has substantially complete solvent action on the oil and substantially no solvent action on the wax, chilling the mixture to a temperature of about -10 F. or lower to precipitate the wax constituents as solid hydrocarbons, and filtering the mixture while maintained in a cold condition to remove the solid hydrocarbons so precipitated.

5. The process of manufacturing low pour test lubricating oil from wax-bearing mineral oil comprising mixing with the oil a selective solvent liquid composed of propylene dichloride in admixture with a liquid selected from the group consisting of ethylene-glycol-mono-ethyl-ether and diethylene, glycol-mono-butyl-ether in such proportions that at temperatures of l0 F. or lower, the solvent has substantially complete solvent action on the oil and substantially no solvent 10 action on the wax, chilling the mixture to a temperature at which the wax constituents are precipitated, and filtering the resulting mixture in the presence of a filter-aid material while maintained in a cold condition to remove the precip- 15 itated wax constituents and produce a desired low pour test lubricating oil product.

6. The process of dewaxing mineral lubricating oil which comprises mixing with the oil a selective solvent liquid composed of an added oil 20 solvent liquid and a wax anti-solvent liquid consisting of ethylene-glycol-mono-ethyl-ether in such proportions that at temperatures of the order of 10 F. the mixture has substantially complete solvent action on the oil but substantially no 25 solvent action on the wax, chilling the mixture to precipitate the wax, separating the wax thus precipitated, and removing the solvent from the resulting dewaxed oil.

7. The process of dewaxing mineral lubricating 30 oil which comprises mixing with the oil a selective solvent liquid composed oi. a mixture of an added oil solvent liquid and a wax anti-solvent liquid consisting of diethyl ne-glycol-monobutyl-ether in such proportions that at tempera- 35 tures of the order of 10 F. the mixture has substantially complete solvent action on the oil but substantially no solvent action on the wax, chilling the mixture to precipitate the wax, separating the wax thus precipitated, and removing 4D the solvent from the resulting dewaxed oil.

8. The process of dewaxing mineral lubricating oil which comprises mixing with the oil a selective solvent liquid composed of a mixture of an added solvent liquid and a wax anti-solvent liquid t selected from the group consisting of the monoalkyl ethers of ethylene and diethylene glycol up to and including the butyl ethers in such proportions that at temperatures of the order of -10 F. the mixture has substantially complete solvent 50 action on the oil but substantially no solvent action on the wax, chilling the mixture to precipitate the wax, separating the Wax thus precipitated, and removing the solvent from the resulting dewaxed oil.

9. The process of dewaxing mineral lubricating oil which comprises mixing with the oil a selective solvent liquid composed of a mixture of an added oil solvent liquid and a wax anti-solvent 60 liquid selected from the group consisting of the mono-alkyl ethers of ethylene and diethylene glycol up to and including the butyl ethers in such proportions that at temperatures of the order of 10 F. the mixture has substantially complete solvent action on the oil but substantially no solvent action on the Wax, chilling the mixture to precipitate the wax, filtering the cold mixture in the presence of a filter-aid material to remove 7 the wax, and removing thesolvent from the resulting filtrate to produce low pour test oil.

BERNARD Y. McCARTY. WILLIAM E. SKELTON. 

